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R J Scott

Publications and source records attributed to R J Scott.

At least 37 records · Page 2Linked to original sources
PubMed2002

BRCA2 gene mutations in families with aggregations of breast and stomach cancers.

Stomach cancer ranks second to lung cancer in the global cancer burden. It is estimated that 25% of families meeting the criteria for hereditary diffuse gastric carcinoma (HDCG) will have germline mutations in the E-cadherin gene. Evidence suggests that stomach cancer might also be a malignant manifestation of other inherited predispositions to disease. Recently, it has been reported that the incidence of stomach cancer is significantly increased in BRCA2 gene mutation carriers. We analysed by direct sequencing the BRCA2 gene in 29 breast cancer patients derived from 29 families with an aggregation of at least one female breast cancer diagnosed before the age of 50 years and one male stomach cancer diagnosed before the age of 55 years. In all but one of these families at least one additional relative was also affected by a malignant tumour. We identified three frameshift mutations and three sequence variants - potentially missense mutations, in six unrelated patients representing 20.7% (six out of 29) of the families investigated. Our results confirm that BRCA2 gene mutations are also associated with familial aggregations of not only breast but also of stomach cancer. In comparison to the number of cancers expected in the study population compared to the general population there is an over-representation of several cancers with significant confidence intervals to suggest that the associations are real and not a selection artefact.

Adult↗
PubMed2002

Integrin expression in colon cancer cells is regulated by the cytoplasmic domain of the beta6 integrin subunit.

We have previously reported that the alphavbeta6 integrin upregulates its own expression in a protein kinase C-dependent manner with increasing cell density. The wild-type beta6 integrin subunit has also been shown to promote tumour growth in vivo and its growth-enhancing effect is regulated by both a MAP kinase binding motif on beta6 and the 11 amino acid C-terminal cytoplasmic extension unique to the beta6 subunit. Herein, we show that the 11 amino acid cytoplasmic extension is essential for the cell density-dependent increase in beta6 expression and that the 11 amino acid tail exerts a dominant negative effect on cell density- and PKC-mediated beta5 expression in alphavbeta6-expressing colon cancer cells. Cells that express beta6 lacking the 11 amino acid tail respond to PKC simulation with increased expression of only the beta5 subunit as seen for cells that lack constitutive alphavbeta6 expression. In contrast, loss of the ERK binding site on beta6 markedly impairs cell density- and PKC-dependent expression of either beta6 or beta5 in the presence or absence of the 11 amino acid tail, respectively. Our findings suggest that in alphavbeta6-expressing cells, a hierarchy of kinase signalling cascades exists and that the beta6-ERK2 interaction dominates over PKC-mediated signalling pathways responsible for integrin upregulation with cell confluence. Given the dominance of the beta6-ERK2 interaction over PKC-mediated expression of both beta5 and beta6 integrin subunits, targeting the beta6-ERK2 interaction may prove useful as an anticancer strategy in colon cancer.

Amino Acid Motifs↗
PubMed2002

Mutation analysis of the STK11/LKB1 gene and clinical characteristics of an Australian series of Peutz-Jeghers syndrome patients.

Peutz-Jeghers syndrome (PJS) is a rare cancer predisposition, which is characterized by the presence of hamartomatous polyposis and mucocutaneous pigmentation. A significant proportion of both familial and sporadic forms of this disorder are associated with mutations in the STK11 (serine/threonine kinase 11)/LKB1 gene. In this report we present a series of Australian PJS cases, which suggest that mutations in the STK11 gene do not account for many families or patients without a family history. The most likely explanation is either the presence of another susceptibility gene or genetic mosaicism in the non-familial patients.

AMP-Activated Protein Kinase Kinases↗
PubMed2002

A novel extinction screen in Arabidopsis thaliana identifies mutant plants defective in early microsporangial development.

Few Arabidopsis mutants defective in early male or female germline development have been reported. A novel extinction screen has been devised which permits the identification of mutants deficient in the earliest stages of anther development. Using mutagenized plants carrying GUS reporter constructs driven by tapetal-specific promoters originally derived from Brassica genes, a wide spectrum of mutants have been identified in Arabidopsis, ranging from those defective in archesporial cell differentiation to others expressed later in development. Crosses between these lines and known anther development mutants have enabled the identification of lines carrying mutations in genes expressed during very early anther formation. Initial characterization reveals these early mutants fall into two classes, gne (GUS-negative) 1-like, and gne2-like. Members of the gne1 mutant class initiate all four layers of the anther wall and an appropriate number of sporogenous cells; however, as development proceeds the tapetal and middle-layer cells enlarge, eventually crushing the sporogenous cells. The gne2 class anthers are disrupted at an earlier stage, with the middle and tapetal layers failing to form, and an excess of sporogenous cells developing until the germline aborts late in meiosis II. Analysis of these mutants has already raised questions about the accuracy of current models of angiosperm anther development.

Arabidopsis↗
PubMed2001

Optimization of experimental conditions for RNA-based sequencing of MLH1 and MSH2 genes.

The most sensitive technique for the detection of germline mutations is exon by exon sequencing of the gene under investigation using genomic DNA as a template for analysis. This approach, however, has cost and sensitivity limitations that can, at least in part, be overcome by RNA-based analysis. Germline mutations of MLH1 and MSH2 are the most frequent cause of the inherited susceptibility to colorectal and other epithelial cancers known as hereditary non-polyposis colorectal cancer (HNPCC). We compared the analysis of the MLH1 and MSH2 genes using mRNA and genomic DNA as starting material from 21 HNPCC patients. All samples were investigated by RT-PCR, sequencing of cDNA and simultaneous sequencing of genomic DNA. The cDNA was generated using specific primers complementary to the ends of MLH1 and MSH2 genes, respectively. Mutations in MLH1 and MSH2 were detected in 11 out of 21 unrelated patients. In 10 out of 11 cases, mutations were detected independently of the type of primers used for reverse transcription (RT). One novel missense mutation (K751R) in MLH1 was detected using this method. One nonsense mutation (E205X) in MSH2 was only detectable when RT was performed using MSH2 gene-specific primers. Shorter PCR products indicative of alternatively spliced transcripts were not observed when MLH1 or MSH2 specific cDNA RT primers were employed to generate template, except in one case where exon skipping was observed for exons 9 and 10. In this report we demonstrate that primers specific for RT of MLH1 and MSH2 are crucial for increasing the sensitivity of cDNA analysis. DNA sequencing using RNA as a basis for template construction may be a valuable and economical alternative to genomic DNA sequencing.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Detection of germline mutations in the BRCA1 gene by RNA-based sequencing.

BRCA1 mutation detection is expensive and has sensitivity limitations, which might at least partially be overcome by RNA-based sequencing. There are claims that RNA tests are unreliable due to differential splicing, exon skipping, or nonsense-mediated mRNA decay that results in either the absence or low expression of mRNA harboring mutations. The major aim of this study was to determine if the application of specific high temperature annealing primers can assure high sensitivity of detection of BRCA1 sequence alterations by cDNA sequencing. The study group comprised 21 Polish cancer families with aggregations of breast and/or ovarian cancer. We detected mutations in 10 out of 21 unrelated patients. These were: nucleotide substitutions (c.309T>C; c.300T>G); nucleotide insertions (c.5382insC) three cases; nucleotide deletions (c.4154delA) one case, (c. 185delAG) one case, (c.3819delGTAAA) two cases; and the deletion of the entire sequence of exon 22, one case. In addition, we identified three transcript variants resulting from alternative splice sites affecting the last six nucleotides of exon 1a (GTAAAG), and the first three nucleotides (CAG) of exon 8 and exon 14. In all cases these were cDNA heterozygous changes. Two of these splice site changes have not been previously described. Sequencing of genomic DNA "exon by exon" did not result in the detection of any additional abnormalities. The sensitivity of our analyses was sufficient to reliably detect mutations without the necessity of tissue culturing to obtain enough template cDNA for analysis.

Alternative Splicing↗
PubMed2001

Relationship between APC genotype, polyp distribution, and oral sulindac treatment in the colon and rectum of patients with familial adenomatous polyposis.

PURPOSE: Familial adenomatous polyposis is an inherited colorectal cancer syndrome characterized by the presence of multiple adenomatous colorectal polyps. Molecular studies have revealed that germline mutations in the APC gene are the underlying cause of the disease. The nonsteroidal anti-inflammatory agent sulindac has been shown to reduce the number of colorectal adenomas. Most sulindac trials in the large bowel have focused on the distal colon and relatively little is known about its effect on the proximal colon. Moreover, it is unknown whether the site of the APC mutation affects the efficacy of sulindac. METHODS: This study investigated whether there were regional differences in the effect of sulindac on the colon and whether response to sulindac was dependent on the site of mutation in the APC gene. In an open prospective study 17 patients with familial adenomatous polyposis were treated with 300 mg oral sulindac daily for four months followed by a washout phase of six months. Ten of the patients had an intact colon and seven had rectal stumps only. The number, size, and the degree of dysplasia of the adenomas were evaluated by colonoscopy at entry, end of treatment and end of the study. RESULTS: Overall, a statistically significant decrease in the number of adenomas was observed (120 +/- 112 to 28 +/- 64, P = 0.007). After cessation of sulindac treatment the number of adenomas increased to 48 +/- 44.5, but remained significantly lower than the values observed at baseline. In the ten patients with intact colons, adenomas decreased by sevenfold in the proximal colon (103 +/- 73 to 15.1 +/- 47.4, P = 0.011) and twofold in the distal colon (80 +/- 52 to 29.6 +/- 37.2, P = 0.005). The size of adenomas and the grade of dysplasia also decreased. No correlation could be seen between the APC mutation site and the response to treatment. CONCLUSION: These data indicate that sulindac reduces the number of adenomas in the entire colon and that the effect seems to be more pronounced in the proximal colon.

Adenomatous Polyposis Coli↗
PubMed2001

The epigenetic basis of gender in flowering plants and mammals.

What makes a sperm male or an egg female, and how can we tell? A gamete's gender could be defined in many ways, such as the sex of the individual or organ that produced it, its cellular morphology, or its behaviour at fertilization. In flowering plants and mammals, however, there is an extra dimension to the gender of a gamete--due to parental imprinting, some of the genes it contributes to the next generation will have different expression patterns depending on whether they were maternally or paternally transmitted. The non-equivalence of gamete genomes, along with natural and experimental modification of imprinting, reveal a level of sexual identity that we describe as 'epigender'. In this paper, we explore epigender in the life history of plants and animals, and its significance for reproduction and development.

Animals↗
PubMed2001

Profuse familial adenomatous polyposis with an adenomatous polyposis coli exon 3 mutation.

The attenuated form of familial adenomatous polyposis coli (AAPC) is associated with mutations in the adenomatous polyposis coli (APC) gene which cluster in the 5' region of the gene. It has been proposed that a 'genotype-phenotype boundary' exists at codons 159-163, and mutations that are 5' of this boundary will produce AAPC. Herein we document a three-generation family with an exon 3 mutation well to the 5' side of the proposed boundary, in which two affected individuals have had, in their 40s, a profuse form of familial adenomatous polyposis coli. We conclude that the codon 159-163 'boundary' is indicative rather than definitive. These two patients also had postoperative intra-abdominal adhesions, severely so in one.

Adenomatous Polyposis Coli↗
PubMed2001

An interaction between the cytochrome P450 probe substrates chlorzoxazone (CYP2E1) and midazolam (CYP3A).

AIMS: The use of multiple probe substrates to evaluate the activity of drug metabolizing enzymes requires that there are no inter-substrate interactions. As part of a series of studies to develop a clinically useful collection of probe substrates that could be given alone or in any combination, we observed an interaction between midazolam (MDZ) and another component of the six-drug cocktail. Published data indicated that the interacting component was likely to be chlorzoxazone. This was investigated as part of a second study. The data relating to the interaction from both studies are reported here. METHODS: Both studies were performed in 16 healthy subjects. All treatments were given orally after an overnight fast. In study 1, which was performed to a four-period, open, crossover design, subjects received on separate occasions MDZ 5 mg, diclofenac 25 mg, a four drug cocktail (caffeine 100 mg, mephenytoin 100 mg, debrisoquine 10 mg and chlorzoxazone 250 mg) and a six drug cocktail (caffeine 100 mg, mephenytoin 100 mg, debrisoquine 10 mg, chlorzoxazone 250 mg, diclofenac 25 mg and MDZ 5 mg). In study 2, which was performed to a two-period, open, crossover design, subjects received a five drug cocktail (as the six drug cocktail in the first study, but without chlorzoxazone and with diclofenac dose increased to 50 mg) and a six drug cocktail (as five drug cocktail, with chlorzoxazone 250 mg). In both studies, blood samples were taken for measurement of plasma MDZ and 1-hydroxy MDZ (1-OH MDZ) concentrations. In study 1, blood samples were taken up to 12 h post-dose while in study 2 a single sample was taken 2 h after dosing. In study 1, the potential interaction between MDZ and the other components of the six drug cocktail was assessed by comparing AUClast ratios (1-OH MDZ/MDZ) between the two treatments. Additionally, a single sampling timepoint of 2 h post-dose for determination of concentration, rather than AUC, ratios was established. The 2 h plasma concentration ratios from studies 1 and 2 were combined and a pooled analysis performed to compare ratios within each study (to determine the change in ratio when MDZ was dosed with and without chlorzoxazone) and between studies (to determine the consistency of the ratios when MDZ was given either as part of the two six drug cocktails or when given alone and as part of the five drug cocktail). RESULTS: In study 1, both the AUClast ratio and the 2 h post-dose plasma concentration ratio were reduced when MDZ was given as part of the six drug cocktail in comparison with those for MDZ alone. This was the result of an increase in MDZ, rather than decrease in 1-OH MDZ, concentrations and was considered to result from a reduction in first pass metabolism of MDZ. The geometric mean AUClast values (with 95% CI) for MDZ were 95.6 (79.0, 115.7) and 160.4 (133.6, 192.6) microg l(-1) h when given alone and as part of the six drug cocktail, respectively. The corresponding values for 1-OH MDZ were 789.6 (697.6, 893.6) and 791.4 (701.7, 892.6) microg l(-1) h. The ratio of adjusted geometric mean AUClast ratios for the two treatments was 1.82 (90% CI 1.48, 2.23, P < 0.001). The pooled plasma 1-OH MDZ/MDZ ratio data from both studies showed that the differences in MDZ metabolism observed in study 1 were replicated in study 2. The adjusted geometric mean 1-OH MDZ/MDZ ratios when MDZ was given alone and as part of the six drug cocktail were 7.79 and 4.59, respectively, for study 1 (ratio 1.70, 95% CI 1.36, 2.11, P < 0.001) and 7.64 and 4.60 for study 2 (ratio 1.66, 95% CI 1.34, 2.06, P < 0.001). These data indicate that when given orally chlorzoxazone interacts with MDZ, increasing plasma MDZ concentrations. In contrast, there was no difference between the plasma 1-OH MDZ/MDZ ratios when MDZ was given alone and as part of the five drug cocktail indicating that there were no interactions between MDZ and any of the other components of that cocktail. CONCLUSIONS: Chlorzoxazone appears to significantly influence the pharmacokinetics of oral MDZ, probably through inhibition of first pass metabolism by CYP3A in the GI tract. Data from these studies and literature evidence showing a further interaction between chlorzoxazone and CYP1A2 substrates and questions concerning the specificity of chlorzoxazone as a probe substrate for CYP2E1, indicate that the use of chlorzoxazone in multisubstrate probe cocktails should be avoided.

Administration, Oral↗
PubMed2001

Familial adenomatous polyposis: more evidence for disease diversity and genetic heterogeneity.

Familial adenomatous polyposis (FAP) is characterised by the presence of profuse colonic carpeting of adenomas throughout the entire colon and rectum. The genetic basis of FAP has been shown to be primarily associated with germline mutations in the APC gene. Notwithstanding, several reports have been published indicating that there is genetic heterogeneity in FAP and that the most likely explanation is the existence of another gene. In this report we further delineate the genotype/phenotype correlation in families that harbour germline mutations in the APC gene and identify some previously unreported changes in the APC gene which predispose to an attenuated disease phenotype. From 53 index patients diagnosed with either FAP or attenuated FAP, 27 harboured changes in the APC gene. The remaining 26 patients were further subgrouped according to their colonic phenotype. There were nine patients with a mixed hyperplastic/adenomatous colonic phenotype and there were 17 patients with an adenomatous colonic phenotype. Evaluation of the disease characteristics of these patients and their families is presented which may aid in the identification of new genes associated with colonic polyposis.

Adenomatous Polyposis Coli↗
PubMed2001

Cell cycle dependent DNA break increase in ataxia telangiectasia lymphoblasts after radiation exposure.

The most striking feature of ataxia telangiectasia (AT) cells is their profound sensitivity to ionising radiation. A deficiency in the rejoining of radiation induced DNA breaks has been suggested to be responsible for AT radiosensitivity; however, the existing literature is controversial. A subpopulation, which is present in irradiated AT lymphoblasts, but rarely in controls, has been reported previously. The cells that make up this subpopulation harbour highly fragmented DNA and are responsible for the overall increase in DNA breaks soon after irradiation in AT lymphoblasts. This study examines the influence of the cell cycle on the highly damaged subpopulation. The frequency of highly damaged cells was highest when AT lymphoblasts were irradiated during the G2/M phase. In contrast, AT lymphoblasts irradiated during the G0/G1 phase displayed a frequency similar to control cells. Thus, only G2/M and to some extent S phase cells contribute to an increased DNA break number in AT lymphoblasts early after irradiation. These findings might explain several inconsistencies reported in the literature.

Adult↗
PubMed2001

Genomic imprinting in plants.

Genomic imprinting, though most extensively studied in mammals, has long been known to perform an important role in seed development in flowering plants. In this chapter, an overview of what is known to date about genomic imprinting in flowering plants and how this knowledge came into being will be given.

Genomic Imprinting↗
PubMed2000

Hereditary nonpolyposis colorectal cancer in 95 families: differences and similarities between mutation-positive and mutation-negative kindreds.

Hereditary nonpolyposis colorectal cancer (HNPCC) describes the condition of a disparate group of families that have in common a predisposition to colorectal cancer in the absence of a premalignant phenotype. The genetic basis of this disease has been linked to mutations in genes associated with DNA mismatch repair. A large proportion of families harbor changes in one of two genes, hMSH2 and hMLH1. Approximately 35% of families in which the diagnosis is based on the Amsterdam criteria do not appear to harbor mutations in DNA-mismatch-repair genes. In this report we present data from a large series of families with HNPCC and indicate that there are subtle differences between families that harbor germline changes in hMSH2 and families that harbor hMLH1 mutations. Furthermore, there are differences between the mutation-positive group (hMSH2 and hMLH1 combined) of families and the mutation-negative group of families. The major findings identified in this study focus primarily on the extracolonic disease profile observed between the mutation-positive families and the mutation-negative families. Breast cancer was not significantly overrepresented in the hMSH2 mutation-positive group but was overrepresented in the hMLH1 mutation-positive group and in the mutation-negative group. Prostate cancer was not overrepresented in the mutation-positive groups but was overrepresented in the mutation-negative group. In age at diagnosis of colorectal cancer, there was no difference between the hMSH2 mutation-positive group and the hMLH1 mutation-positive group, but there was a significant difference between these two groups and the mutation-negative group.

Adolescent↗
PubMed2000

Characterisation of autoantibodies to peripheral myelin protein 22 in patients with hereditary and acquired neuropathies.

To investigate the possibility that an autoimmune mechanism may play a role in the hereditary neuropathy Charcot-Marie-Tooth type 1A (CMT1A), sera were analysed by Western blot for anti-peripheral myelin protein 22 (PMP22) autoantibodies. These sera were compared with sera from patients with CMT type 2 (CMT2), acquired peripheral neuropathies such as chronic inflammatory demyelinating neuropathy (CIDP), anti-MAG IgM neuropathy, Miller-Fisher syndrome (MFS), diabetic neuropathy and with control blood donors. Anti-PMP22 positive sera were detected in 70% of patients with CMT1 and unexpectedly in 60% of patients with CMT2. Interestingly, 44% of the patients with other peripheral neuropathies and 23% of the apparently healthy controls showed also anti-PMP22 antibody reactivity. Immunohistochemical analysis of the human anti-PMP22 antisera on healthy sural nerve sections and on PMP22-expressing COS cells revealed that these sera did not recognise endogenous PMP22. Our results indicate that anti-PMP22 autoantibodies are found in sera of patients with different types of peripheral neuropathies, but their role in the pathogenesis of these diseases remains to be determined.

Adult↗